A tornado poses a great danger to persons and property in its vicinity. In the United States alone, tornadoes result in tens of millions of dollars in property damage every year. In addition, tornadoes result in the deaths of numerous people every year.
One of the reasons that tornadoes are so dangerous is that they often occur very quickly and with very little discernible warning. Lives can often be saved if a person in the path of a tornado can take shelter in a relatively safe place, e.g., a basement or shelter. Thus, to minimize the loss of life, it is advantageous to provide people in the vicinity of a tornado with the earliest possible warning of the tornado, increasing the likelihood that the people will be able to take shelter in time.
It is well-known that tornadoes produce electromagnetic signals. Among the various conventional types of tornado warning systems are several approaches that seek to detect tornadoes by detecting the electromagnetic signal generated by the tornado. For instance, U.S. Pat. No. 4,684,951 to Baumer (hereinafter referred to as “Baumer”) discloses a process and apparatus for monitoring weather phenomena, such as tornadoes. The apparatus of Baumer receives multiband very low frequency (“VLF”) electromagnetic radiation, i.e., 3 kHz to 100 kHz, in the atmosphere. The apparatus then splits the frequency into two bands, and compares the received frequencies with frequency values for known atmospheric events.
U.S. Pat. No. 4,023,408 to Ryan et al. (Hereinafter referred to as “Ryan et al.”) discloses a storm mapping system that detects electrical disturbances generated by weather phenomena. The system of Ryan et al. receives electrical signals generated by the weather phenomena in a predetermined frequency band. The system then employs the absolute signal intensity and provides a display of the signals to an observer so as to be relative to the signal's magnitude.
U.S. Pat. No. 4,812,825 to Kennedy et al. (Hereinafter referred to as “Kennedy et al.”) discloses a tornado warning system that employs a superheterodyne receiver to detect electromagnetic signal generated by a tornado. The system of Kennedy et al. is tuned to a single frequency. If a signal of this frequency is detected by the system of Kennedy et al., at a predetermined strength for a predetermined length of time, an alarm is triggered.
However, none of these tornado warning systems, nor other conventional tornado warning systems that employ the electromagnetic signal generated by a tornado, adequately detect tornadoes.